A plain tsuba is a sword guard with no decorative carving, inlay, piercing (sukashi), or applied metalwork on its surface. The form is typically circular or oval, finished in iron or iron alloy, and valued for its visual restraint. In Japanese sword history, plain tsuba were associated with practical or scholarly tastes - a preference for silhouette and material quality over ornamentation. For display collectors today, the plain guard is significant because it draws attention to the blade's geometry, the hamon line, and the overall balance of proportions rather than fragmenting the eye across multiple decorative focal points. It is a style choice with historical precedent, not simply a budget simplification.